1. Field of the Invention
The present invention relates generally to power management, and more particularly to a method of reducing power consumption in a portable IP (Internet Protocol) communications device, e.g., a multimode device such as a cellular telephone with Internet communication capabilities.
2. Description of Related Art
Continued advancements in telecommunication technologies and Internet technologies have made portable devices with IP capabilities, including cellular telephones with Internet access, very popular. Since talk time and standby time are important performance attributes of such devices, techniques for extending battery life or otherwise reducing power consumption are becoming increasingly important.
FIG. 1 illustrates an exemplary architecture 100 of an existing dual mode cellular/Wi-Fi phone chipset. As shown, the architecture 100 may have an application processor (AP) 101, a Wi-Fi chipset 102 and a cellular modem 103. The application processor 101, which may be an ARM processor, for example, typically may run at frequencies as high as 400-600 MHz, and is a high performance and high-power consumption device. The more the processor 101 is on, the more battery power the processor 101 will drain. The Wi-Fi chipset 102 may communicate with the application processor 101 via an SDIO (Secure Digital Input/Output) interface 104, and the cellular modem 103 may communicate with the application processor 101 via a UART (Universal Asynchronous Receiver/Transmitter) interface 105. The architecture 100 may also include a RAM (Random Access Memory) 106, a DMA (Direct Memory Access) 107, and a bus 108 coupling various components in the architecture 100. The whole IP stack may reside in the application processor 101, which may control all Wi-Fi operation, including link maintenance and message broadcasting. VoIP (Voice over Internet Protocol) is controlled by the application processor 101 as well.
One problem with the architecture 100 shown in FIG. 1 is that the application processor 101, running at relatively high frequencies, may have to be running at full power constantly because of the various functions the application processor 101 performs, thereby resulting in shorter battery life. Even though, for example, processing telephone communications through cellular modem 103 does not require constant activity (for example, in some known implementations, communication is on for a short period of time, such as 20 ms, and then off for a comparable period of time), the application processor 101 may have to be awake during the whole call because of processing of data from Wi-Fi chipset 102. Thus, even when no data is being communicated through the cellular modem 103, the Wi-Fi chipset 102 may be involved in handling and maintaining a status of various network level protocols, e.g., TCP (Transmission Control Protocol), IPv4, IPv6 and UDP (User Datagram Protocol). The architecture 100 of FIG. 1 may have to keep the application processor 101 awake to implement such network protocols. For example, for the Wi-Fi chipset 102 to operate at peak performance, the application processor 101 may have to control the following operations: 1) scanning the radio environment for available access points; 2) connecting to access points in a Wi-Fi communications network capable of providing the best bandwidth and QoS (Quality of Service); 3) sending “keep alive” packets to the Wi-Fi access points to maintain connectivity; and 4) responding and digesting broadcast messages from the Wi-Fi access points. These operations may require considerable processing time of the application processor 101, and consequently may cause significant battery drain.